Gambit Bay is the water the Ultimate boat is pitched for. It confirms fishing as an activity, alongside the diving and water sports shown in the Extended Look.
The edition text says the Squalo is 'perfect for casting in Gambit Bay and reeling in catches of all sorts.' Fishing also turned up in the Extended Look, and Rockstar promotes Mount Kalaga with fishing too. Rockstar has not placed Gambit Bay on a map.